Finishing wet concrete to a smooth, even, flat surface is time and labor intensive. Creating a smooth surface is particularly important when pouring surfaces that will be walked on, such as floors, walkways, driveways and stair cases.
The first step in smoothing out poured concrete is to flatten the concrete using a “screed”. A screed is typically a long, straight wooden board. The screed is dragged across the poured cement while simultaneously holding the board against the edges of the form. By repeating both sweeping and wriggling motions of the screed as it is passed over the concrete surface, areas of excess cement are pushed into lower points until the surface is sufficiently smooth. The screed is typically a 2 inch by 4 inch piece of lumber. While lumber is inexpensive, most pieces of lumber are slightly warped due to moisture and temperature, and as a result, are not straight-edged. The lumber can also be heavy and awkward to slide and push across the cement surface. The thick lumber also often catches on the wet surface and creates imperfections.
To avoid the problems with wood, some concrete finishers use aluminum screeds comprising straight lengths of aluminum with sharp edges. The aluminum is lighter to lift and move across the surface.
After the screed flattens the wet concrete, a second tool called a “float” may be used to push the surface and compress the concrete. Floats are typically large flat plates connected to handles. Floats are used, in particular, with concrete that has large pieces of aggregate. In the case of pure cement, floats help to not only squeeze water from the mix, but also to complete the smoothing out of the slab. Floats essentially consolidate a slab by pushing aggregates towards the center of the slab while bringing paste to the surface. Floats are typically constructed from wood or magnesium (referred to as a “mag float”). Magnesium floats are used, in particular, to close concrete surfaces when the concrete mix contains an air entraining admixture.
Creating smooth stair treads (stair steps) poses unique problems. Concrete stairways are typically formed by angled wooden stringers on both sides of the stair-well connected to spaced, vertically-oriented risers. Concrete is poured into the form. Because the angled stringers form the sides of each step, a traditional flat screed and/or float may not be used against the edges of opposing forms to smooth out and finish the stair treads. Instead, each stair tread must be separately smoothed out and finished by hand typically with use of a flat cement trowel.
Use of a trowel to smooth out each step is time and labor intensive due to the amount of cement that has to be smoothed out before the cement may be finished. In addition, the tool operator must hold the trowel and operate the trowel in close proximity to the wet cement surface for relatively long periods of time, which poses access problems when the stairway is lengthy or otherwise out of the close reach of the worker. In that event, the worker must wait for a series of steps to dry and harden before accessing additional steps to smooth out. The timing and difficulty of successive cement pourings adds expense and labor to the job. Alternately, the worker must erect a platform above the stairway upon which the worker may reach out and over each stair tread to smooth the tread out from above.
The base corners between the stair treads and the vertical risers of the next stair step also present a challenge to smoothing out and finishing the wet concrete. The corner should be continuous and smooth. The corner may be set back relative to the stair's toe kick (a small overhang on the outward edge of each stair tread). Forming a flat and smooth surface back to the corner is extremely difficult and usually requires labor intensive use of a hand-held trowel.
Concrete steps are designed in many different shapes and sizes, including curved stairways. As a result, the horizontal length of the stair tread, the vertical height of the stair step, and the shape of the corner differ from one project to the next. The height of each stair step is often determined by measuring the overall vertical height of the stairway and dividing that amount into equal step heights. Stair treads may be similarly determined by measuring the overall lateral distance for the stairway and dividing that amount into equal tread lengths. As a result, any particular stairway may have an entirely unique tread length and step height. The uniqueness of each project typically demands use of the labor and time intensive cement trowel.
Accordingly, there is an unmet need in the art for a combined screed and float device that does not require excessive labor to operate, that quickly and adequately smoothes stair tread wet concrete between stringers, that provides a continuous and clean corner edge between the tread and the riser of the next stair step, that is wide enough to provide a smooth surface and act as a float, but does not catch on the cement, leaving a smooth surface for finishing, and that is adjustable to any range of step heights, tread lengths, and corner shapes to accommodate any conceivable concrete stair project.